With the United States poised to advance to the round of 16 with a win or a tie, many fans will take the day off, or at least enjoy an extended lunch. Work can wait, they say. After all, the World Cup only comes every four years.

The strong performance by the US team so far — a heartbreaking draw with Portugal notwithstanding — has sparked enormous interest, winning huge mainstream appeal that seems to have taken the sport to a new level.

Sunday’s US-Portugal match drew an audience of nearly 23 million at its peak, making it the most-viewed soccer game ever in the United States. In Boston, the game drew an 11.5 rating, fourth-largest in the country behind Washington, D.C., Columbus, Ohio, and New York.

Excluding NFL and college football games, it was the most viewed telecast in ESPN history.

In Boston sports bars featuring World Cup games, the US matches have brought droves of pumped-up fans in patriotic garb — team jerseys, scarfs, bandanas, even flag-like capes.

“Everyone’s coming out dressed to the nines,” said Chuck Hitchcock, general manager at McGreevy’s, an Irish pub and sports bar in the Back Bay. “The energy in the room has been amazing.”

On Sunday, fans arrived hours before the late-afternoon game, he said.

Fans celebrate soccer as a great sport in any setting. But watching in a energized crowd that lives and dies with every scoring opportunity takes it to another level, they said.

“I can’t even imagine just watching ESPN at home.” said Harrington, 30, who lives in Jamaica Plain. “Whenever a goal is scored it’s just chaos.”

Fans said that interest in soccer has been on the upswing for years, bringing the sport from the fringes to the mainstream, particularly during the World Cup, soccer’s grandest stage.

But this year, when even baseball-oriented bars air the Croatia-Mexico game, feels different, fans said.

AJ Andreucci, 22, said the World Cup has become more of a media event in the United States this time around, leading to wall-to-wall coverage of the tournament.

“There’s been a lot more hype,” he said.

Andreucci, a graduate student, agreed to work Saturday in exchange for having a day off Thursday. An easy decision, he said.

Brian Bilello, president of the New England Revolution, the Major League Soccer team, said the national fan base has grown steadily since 1994, when the United States hosted the World Cup and advanced to the round of 16 for the first time since 1930.

The attendance of nearly 3.6 million — including games in Foxborough —
broke the previous World Cup record by more than 1 million.

“That was really the seed,” he said. “You had a boost of interest in all levels of the sport.”

Since the 2002 World Cup, attendance at MLS games has nearly tripled, he said.

Bilello said soccer has become especially popular among fans in their 20s, who cherish the shared experience of cheering on their team, often chanting and singing throughout.

“It’s a very communal sport from the fan perspective,” he said. “I think that’s why it’s resonating right now. People don’t want to be at home watching the game on TV.”

Since the 2014 World Cup began, watch parties have sprung up across the country. In Chicago, some 20,000 people showed up for an outdoor viewing Sunday, with many more turned away when the event reached capacity.

McNamara, 26, said he learned to love the sport while studying abroad in Spain. In person, the games were electric, and he was hooked. “It was fantastic,” he recalled.

Like many fans, McNamara said he has enjoyed seeing fans rally around the US team, which he gives a fighting chance against Germany.

“It’s personally gratifying,” he said. “It’s really cool to see so many people who are genuinely interested in this.”

For devoted fans, the strong play of the US team has given rise to lofty hopes. So when Portugal tied the match in the waning seconds Sunday, the crowd at The Banshee fell silent. For about 10 seconds, no one said a word.

Then the popular chant “I Believe,” broke out, quickly filling the bar. There was another game to come, and maybe more.